Micro-gas generation

ABSTRACT

A gas generant composition used in pressure activated restraint system devices such as micro-gas generator applications such as seat belt pretensioners is provided. The gas generant composition includes a potassium perchlorate gas generant additive in addition to a non-azide nitrogen-containing gas generating fuel, a metal ammine nitrate oxidizer, and a metal oxide burn rate enhancing and slag formation additive. The gas generant composition desirably has improved ignitability as compared to a similar composition without the potassium perchlorate gas generant additive. The gas generant composition also desirably produces or results in effluents having either or both reduced carbon monoxide and NO x  contents as compared to the effluent produced or resulting from a similar composition but without the inclusion of the potassium perchlorate gas generant additive.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The subject matter of this application is related to prior U.S.patent application Ser. No. 09/221,910, filed on Dec. 28, 1998, now U.S.Pat. No. 6,103,030, issued Aug. 15, 2000; application Ser. No.09/391,163, filed on Sep. 8, 1999, now U.S. Pat. No. 6,083,331, issuedJul. 4, 2000; and application Ser. No. 09/454,041, filed on Dec. 3,1999, now U.S. Pat. No. 6,224,697, issued May 1, 2001. The disclosuresof each of these related patent applications are hereby incorporated byreference herein in their entirety and made a part hereof including, butnot limited to, those portions which specifically appear hereinafter.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to gas generant compositionsand, more particularly, to gas generant compositions particularly suitedfor use in micro-gas generator devices such as for seat beltpretensioning as well as devices, systems and methods of gas generationusing or employing such gas generant compositions.

[0003] Various safety restraint systems for the protection of vehicleoccupants have come into widespread use. In such systems, a restraintdevice is typically actuated upon the occurrence of a condition duringwhich a vehicle occupant is to be restrained. As will be appreciated, avehicle collision is an example of a common occurrence for whichrestraint of a vehicle occupant is customarily desired.

[0004] A common type or form of vehicular actuatable occupant restraintsystem has or includes a seat belt which is extendable across thevehicle occupant and includes an actuatable device, such as apretensioner, provided to move at least a portion of the seat beltrelative to the occupant. For example, one modern seat belt is known asa 3-point restraint because it is secured to the vehicle at three pointsarranged about the vehicle occupant to provide a diagonal torso sectionand a horizontal lap portion to hold the vehicle occupant in the seat.The belt is customarily attached to the vehicle by a spring-loadedretractor tending to tighten the belt, and by a buckle for quick releaseof the belt. Seat belt pretensioners are typically sited at theretractor or at the buckle end of the restraining seat belt. Seat beltpretensioners are commonly designed to store energy which, whenreleased, effects the pretensioning operation. This energy may bemechanical energy such as in the form of a stressed spring but, morecommonly, modern pretensioners are typically pyrotechnically operated.Pyrotechnically-operated pretensioners commonly comprise a sealed tubecontaining a gas generant composition which reacts rapidly to generategas and rapidly expand to provide the energy to effect the pretensioningoperation. For example, such generated gas may be used to drive a pistonor the like, such as included or used in a pretensioner, in associationwith a seat belt or other restraint device. In view of the relativelysmall amount of gas generated or produced from, in or by such devices,as compared to gas generating inflators typically used in the inflationof inflatable restraint system airbag cushions, such devices arecommonly referred to as “micro-gas generators.”

[0005] Micro-gas generators are generally composed of a single housingwhich contains an initiation element such as in the form of squib, anintermediate igniter composition and a high output, gas generatingmaterial. Squibs used in such devices typically include a heatedbridgewire to which has been applied a thermally sensitive very hotburning initiator composition, however, other known initiation elementscan, if desired be used. Thus, micro-gas generators are typically verysmall devices which generally contain components corresponding to thosecontained in an airbag inflator, including an initiation element, anigniter composition and a high output, gas generating material, butwithout the degree of physical separation typically present in airbaginflators. Further, due to the very small operating time requirementsassociated with micro-gas generator applications (such as operatingtimes of about 6 milliseconds or less), such devices generally contain amuch larger ratio of igniter material to gas generating material, ascompared to typical airbag inflator devices. For example, inflators usedin association with the inflation of frontal impact airbag cushionsemployed for driver protection typically contain or include ignitermaterial in a range of about 3-10% by weight of the total gas producingmaterial (e.g., igniter material and gas generating output charge)present in the inflator device. In contrast, in micro-gas generators,the igniter material may generally be present within the device in arelative amount of at least about 20% by weight of the total gasproducing material present therewithin and typically in a range of about20-50% by weight of the total gas producing material present in thedevice.

[0006] Gas generant compositions commonly utilized in the inflation ofautomotive inflatable restraint airbag cushions have previously mosttypically employed or been based on sodium azide. Such sodiumazide-based compositions, upon initiation, normally produce or formnitrogen gas. While the use of sodium azide and certain otherazide-based gas generant materials meets current industryspecifications, guidelines and standards, such use may involve or raisepotential concerns such as involving the safe and effective handling,supply and disposal of such gas generant materials.

[0007] Certain economic and design considerations have also resulted ina need and desire for alternatives to azide-based pyrotechnics andrelated gas generants. For example, interest in minimizing or at leastreducing the overall space requirements for inflatable restraint systemsand particularly such requirements related to the inflator component ofsuch systems has stimulated a quest for gas generant materials whichprovide relatively higher gas yields per unit volume as compared totypical or usual azide-based gas generants. Further, automotive andairbag industry competition has generally lead to a desire for gasgenerant compositions which satisfy one or more conditions such as beingcomposed of or utilizing less costly ingredients or materials and beingamenable to processing via more efficient or less costly gas generantprocessing techniques.

[0008] As a result, the development and use of other suitable gasgenerant materials has been pursued. In particular, such efforts havebeen directed to the development of azide-free gas generants for use insuch inflator device applications. In view of the above, there is a needand a desire for an azide-free gas generant material that, whileovercoming at least some of the potential problems or shortcomings ofazide-based gas generants, may also provide relatively high gas yields,such as compared to typical azide-based gas generants. In particular,relatively low cost gas generant material solutions to one or more suchproblems or limitations are desired.

[0009] As will be appreciated, a desirable feature of micro-gasgenerator devices used in or in connection with seat belt pretensioningis the production of a relatively large quantity of gas from arelatively small volume. In addition, it is desirable that such gasgenerator devices minimize or avoid the production of substantialamounts of possibly undesirable effluent gases such as carbon monoxideand nitrogen-containing oxides such as in the form of NO_(x), e.g., NOand NO₂, for example, and which undesirable effluent gases might somehowescape into the vehicle interior and thus come into contact with theoccupant(s).

[0010] Gas generant materials and compositions, such as disclosed in theabove-identified related applications, now U.S. Pat. No. 6,103,030; U.S.Pat. No. 6,083,331; and U.S. Pat. No. 6,224,697, can generally provide acombination of high flame temperature (c.a. 2100 K) and gas output(e.g., gas outputs of about 3.3 moles per 100 grams of material) such asrequired or desired for use in micro-gas generators such as for seatbelt pretensioning. However, such gas generant materials commonlyrequire the inclusion of an auxiliary pyrotechnic material, e.g., anigniter material, in order to satisfy one or more performancerequirements, such as for operation at low temperatures, e.g.,temperatures down to −40° C., if such materials are to be used in suchoperations. Unfortunately, the requirement for inclusion of an ignitermaterial, such as in a granulated form, can complicate system design andoperation while also undesirably increasing the costs associatedtherewith. For example, since gas generant material particles aretypically relatively large as compared to igniter material particles,the packaging together of igniter material and gas generant materialparticles commonly results in igniter material particles migrating tothe bottom of the bed of gas generant material and away from the squib.Consequently, such devices may experience undesirably erratic and/orvariable ignition as, for example, the amount of igniter materialmigrating and/or the extent of migration of the igniter material mayvary from device to device. In view thereof, it is common to separatelycontain the igniter material in close proximity to or with the squibsuch that, upon actuation, the igniter material is routinely rapidly andcompletely ignited and provides sufficient energy to uniformly ignitethe gas generant material. Unfortunately, satisfaction of the need tomaintain separation of the igniter material and the main body of gasgenerant material while the device is in a pre-actuation state,typically requires the inclusion of an additional part or component inthe device. As will be appreciated, inclusion of such an additionalcomponent may undesirably increase one or more of the weight, size andcost of the device.

[0011] Thus, there is a need and a demand for improvements in gasgenerant compositions particularly suited for use in micro-gas generatordevices such as for seat belt pretensioning as well as corresponding orassociated improved gas generation devices, systems and methods. In thisregard, there is a particular need and demand for such gas generantcompositions and corresponding or associated improved gas generationdevices, systems and methods, which, in addition to satisfyingrequirements for such micro-gas generator application such as relatingto flame temperature and gas output, also desirably avoid a need orrequirement for the presence or inclusion of an auxiliary pyrotechniccompound, such as an igniter, in order to meet performance requirementssuch as relating to low temperature operation, where low temperatureoperation generally refers to operation at temperatures below ambient,e.g., 25° C., to as low as about −40° C., for example. Further, there isa need and a demand for improvements in gas generant compositionsparticularly suited for use in micro-gas generator devices and which gasgenerant compositions desirably produce or result in gaseous effluentshaving a suitably reduced or lower content of undesired effluent gasessuch as carbon monoxide and NO_(x), for example.

SUMMARY OF THE INVENTION

[0012] A general object of the invention is to provide an improved gasgenerant composition particularly suited for use in micro-gas generatordevices such as for seat belt pretensioning as well as corresponding orassociated improved gas generation devices, systems and methods.

[0013] A more specific objective of the invention is to overcome one ormore of the problems described above.

[0014] The general object of the invention can be attained, at least inpart, through a gas generant composition which composition, inaccordance with one preferred embodiment, contains or includes: betweenabout 25 and about 60 composition weight percent non-azidenitrogen-containing gas generating fuel, between about 10 and about 55composition weight percent metal ammine nitrate oxidizer, between about0 and about 50 composition weight percent ammonium nitrate supplementaloxidizer component, between about 2 and about 10 composition weightpercent metal oxide burn rate enhancing and slag formation additive, andbetween about 1 and about 20 composition weight percent potassiumperchlorate gas generant additive.

[0015] The prior art generally fails to provide a gas generantcomposition which, in addition to satisfying performance requirementsrelating to application in micro-gas generators, such as relating toflame temperature and gas output, also desirably avoids a need orrequirement for the presence or inclusion of an auxiliary pyrotechniccompound, such as an igniter, in order to meet performance requirementssuch as relating to low temperature operation (e.g., operation attemperatures down to −40° C.). The prior art inclusion of an igniterauxiliary pyrotechnic compound has generally resulted in the inclusionof an additional part or component in corresponding gas generatordevices and such as may undesirably increase one or more of the weight,size or cost of the such devices. Further, the prior art has generallyfailed to provide such gas generant compositions which produce or resultin gaseous effluents having a suitably reduced or lower contents ofundesired effluent gases such as carbon monoxide and nitric oxide and asmay be desired for particular applications, such as including inmicro-gas generators used in seat belt pretensioning.

[0016] The invention further comprehends, in accordance with anotherpreferred embodiment a gas generant composition which contains orincludes: between about 25 and about 60 composition weight percentguanidine nitrate, between about 10 and about 55 composition weightpercent copper diammine dinitrate, between about 0 and about 50composition weight percent ammonium nitrate supplemental oxidizercomponent, between about 2 and about 10 composition weight percent metaloxide burn rate enhancing and slag formation additive selected from thegroup consisting of SiO₂, Al₂O₃ and mixtures thereof, and between about1 and about 20 composition weight percent potassium perchlorate gasgenerant additive.

[0017] The invention still further comprehends a seat belt pretensionergas generant composition which contains or includes: between about 25and about 60 composition weight percent guanidine nitrate, between about10 and about 55 composition weight percent copper diammine dinitrate,between about 0 and about 50 composition weight percent ammonium nitratesupplemental oxidizer component, between about 2 and about 10composition weight percent metal oxide burn rate enhancing and slagformation additive selected from the group consisting of SiO₂, Al₂O₃ andmixtures thereof, and between about 4 and about 10 composition weightpercent potassium perchlorate gas generant additive.

[0018] The invention yet still further comprehends an occupant restraintsystem device which includes a housing containing a supply of reactantmaterial. In accordance with a preferred embodiment of the invention,the reactant material includes a fuel component containing between about25 and about 60 composition weight percent of a non-azidenitrogen-containing gas generating fuel, between about 10 and about 55composition weight percent metal ammine nitrate oxidizer, between about0 and about 50 composition weight percent ammonium nitrate supplementaloxidizer component, between about 2 and about 10 composition weightpercent metal oxide burn rate enhancing and slag formation additive, andbetween about 1 and about 20 composition weight percent potassiumperchlorate gas generant additive.

[0019] The invention also yet still further comprehends a method ofgenerating gas suitable for use in an occupant restraint system of amotor vehicle. In accordance with a preferred embodiment of theinvention, such method involves directly igniting a reactant materialincluding a fuel component containing between about 25 and about 60composition weight percent of a non-azide nitrogen-containing gasgenerating fuel, between about 10 and about 55 composition weightpercent metal ammine nitrate oxidizer, between about 0 and about 50composition weight percent ammonium nitrate supplemental oxidizercomponent, between about 2 and about 10 composition weight percent metaloxide burn rate enhancing and slag formation additive, and between about1 and about 20 composition weight percent potassium perchlorate gasgenerant additive.

[0020] Other objects and advantages will be apparent to those skilled inthe art from the following detailed description taken in conjunctionwith the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a simplified schematic, in a partially broken away view,of a micro-gas generator device in accordance with one embodiment of theinvention.

[0022]FIG. 2 is a graphical depiction of tank pressure as a function oftime performance realized in Comparative Example 1 and Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention provides a gas generant material used inpressure activated restraint system devices such as micro-gas generatorapplications such as seat belt pretensioners.

[0024] Turning to FIG. 1, there is illustrated an occupant restraintsystem device, having the form of a micro-gas generator device,generally designated by the reference numeral 10, in accordance with onepreferred embodiment of the invention. In particular, the micro-gasgenerator 10 is shown as having the general form of a device such as mayfind desirable application in the driving of a piston or the like suchas may be desired in a seat belt pretensioner or like apparatus.

[0025] The micro-gas generator 10 includes a housing 12 forming achamber 14. The housing 12 is at least in part defined by an elongatedgenerally cylindrical sleeve 16, having an open first end 20 and aclosed second end 22 and may desirably be formed in a one piececonstruction. As will be appreciated, such a construction desirably mayserve to reduce or eliminate the number of welds needed or used in theconstruction such as by eliminating the need for the welding of an endclosure such to close one or more ends of the housing 12.

[0026] An initiator, generally designated by the reference numeral 24,such as in the form of a heated bridgewire squib is suitably joined orotherwise connected to the sleeve first end 20 and such as to close suchfirst end. The initiator 24 includes or has two electrode pins 26 and28. The electrode pins 26 and 28 are in signal receiving communicationwith one or more sensors (not shown) such as known in the art and suchas effective to send a signal to the initiator 24 to effect the desiredactuation thereof.

[0027] As will be appreciated by those skilled in the art and guided bythe teachings herein provided, other suitable forms of initiatordevices, such as known in the art, can if desired be used in thepractice of the invention. For example, such other suitable forms ofinitiator devices can include spark-discharge, heated or exploding wireor foil and through bulkhead initiators, and may, if desired, optionallycontain a desired load of a suitable pyrotechnic charge. Thus, it is tobe understood that the broader practice of the invention is notnecessarily limited to the incorporation and/or use of a heatedbridgewire squib.

[0028] The housing 12 contains or otherwise includes a supply of gasgenerant composition, generally designated by the reference numeral 30.As described in greater detail below and in accordance with a preferredembodiment, the invention desirably employs a gas generant compositionwhich, in addition to satisfying the stringent demands relating tomaterials employed in micro-gas generators such as in the form of seatbelt pretensioners, also desirably does one or more of the following:

[0029] a) avoids the need for the inclusion of an auxiliary pyrotechniccompound, e.g., an igniter, in order for the device to meet or otherwiseappropriately satisfy performance requirements, such as for operation atlow temperatures, e.g., operation at temperatures below ambient, e.g.,25° C., to as low as about −40° C., for example, and

[0030] b) produces or results in gaseous effluents having a suitablyreduced or lower contents of undesired effluent gases such as carbonmonoxide and NO_(x), for example.

[0031] Gas generant compositions in general accord with the inventiondesirably include a fuel component, an oxidizer component, a burn rateenhancing and slag formation additive and potassium perchlorate gasgenerant additive. More particulary, preferred gas generant compositionsin accordance with the invention desirably include or contain betweenabout 25 and about 60 composition weight percent of a non-azidenitrogen-containing gas generating fuel, between about 10 and about 55composition weight percent of a metal ammine nitrate oxidizer, betweenabout 0 and about 50 composition weight percent ammonium nitratesupplemental oxidizer component, between about 2 and about 10composition weight percent of a metal oxide burn rate enhancing and slagformation additive, and between about 1 and about 20 composition weightpercent potassium perchlorate gas generant additive.

[0032] As identified above, preferred fuel materials for use in thepractice of the invention are non-azide in nature. Groups or categoriesof fuels useful in the practice of the invention include variousnitrogen-containing organic fuel materials and tetrazole complexes of atleast one transition metal. Specific examples of nitrogen-containingorganic fuel materials useful in the practice of the invention includeguanidine nitrate, aminoguanidine nitrate, triaminoguanidine nitrate,nitroguanidine, dicyandiamide, triazalone, nitrotriazalone, tetrazolesand mixtures thereof. Tetrazole complexes of transition metals such ascopper, cobalt, and possibly zinc, for example, can be used. As will beappreciated, the gas generating fuel component of particular gasgenerant compositions in accordance with the invention may be comprisedof individual such fuel materials or combinations thereof.

[0033] In addition, the fuel component of the subject gas generatingmaterial may, if desired, include a metallic fuel material. Specificexamples of metallic fuels useful in the practice of the inventioninclude silicon, aluminum, boron, magnesium, alloys of aluminum andmagnesium and combinations thereof.

[0034] The fuel component of the subject gas generating material, inaccordance with certain particularly preferred embodiments of theinvention, includes the fuel materials guanidine nitrate or guanidinenitrate in combination with one or more metallic fuels of silicon,aluminum, boron, alloys of aluminum and magnesium alloys andcombinations thereof. As will be appreciated, such metallic fuels maydesirably be utilized in a powder form such as to facilitate mixing andcombination with other composition components. While the inclusion ofsuch metallic fuels can serve various purposes, in general such metallicfuels may desirably be included in such compositions to increase thecombustion temperature of the resulting composition.

[0035] In practice, guanidine nitrate is a generally particularlypreferred fuel due to one or more various factors including: having arelatively low commercial cost; generally avoiding undesired complexingwith copper or other transition metals which may also be present; isitself relatively highly oxygenated and thus may serve to minimize orreduce the amount of externally provided oxidant required forcombustion. When included, the powders of silicon, aluminum, boron,alloys of aluminum and magnesium alloys and combinations thereof maygenerally desirably be present in an amount of up to about 5 weightpercent of the total gas generant composition.

[0036] In accordance with certain preferred embodiments of theinvention, between about 10 and about 55 weight percent of the subjectgas generant composition constitutes a metal ammine nitrate oxidizer.Preferred metal ammine nitrate oxidizer materials for use in thepractice of the invention include copper diammine dinitrate, zincdiammine dinitrate and combinations thereof, with copper diamminedinitrate being particularly preferred.

[0037] The subject gas generant compositions additionally desirablycontain between about 2 and about 10 composition weight percent of suchmetal oxide burn rate enhancing and slag formation additive. Examples ofparticular metal oxide burn rate enhancing and slag formation additivesuseful in the practice of the invention include silicon dioxide,aluminum oxide, titanium dioxide, boron oxide and combinations thereof.In general, silicon dioxide, aluminum oxide and combinations thereof arepreferred metal oxide additives for use in the practice of theinvention. The use of the metal oxide is as a burn rate enhancer and forthe purpose of producing slag which is easily filtered from the gasstream of an airbag inflator. The incorporation and use of such siliconand aluminum oxide materials are particularly effective in facilitatingthe production of a slag material which is relatively easily filteredfrom the gas stream of an airbag inflator.

[0038] In the practice of the invention, it is believed that thecombination of such metal oxide component and the relatively high levelsof metal amine nitrate present in the composition taken together areresponsible for the high burning rate and the low burning rate pressureexponent of the compositions.

[0039] Preferred gas generant compositions in accordance with theinvention desirably include or contain between about 1 and about 20composition weight percent potassium perchlorate gas generant additive.In certain particularly preferred gas generant compositions of theinvention such potassium perchlorate gas generant additive is present inan amount of between about 4 and about 10 composition weight percent. Inparticular, advantages attendant the gas generant composition presenceor inclusion of potassium perchlorate gas generant additive inaccordance with the invention generally become more pronounced and moresignificant wherein such potassium perchlorate gas generant additive ispresent in an amount of at least about 4 composition weight percent.Further, the gas generant composition inclusion of such potassiumperchlorate gas generant additive in an amount of more than about 10composition weight percent may undesirably reduce the gas yieldresulting from reaction of the composition.

[0040] Those skilled in the art and guided by the teachings hereinprovided will appreciate that potassium perchlorate is desirablycompatible with other ingredients of the composition. That is, there isgenerally no undesired chemical reaction between potassium perchlorateand other composition components under normal service conditions (e.g.,temperatures of ≦107° C.) until such time as combustion is initiated.More particularly, for example, the potassium perchlorate is desirablyanhydrous in form as hydrated materials can undesirably react withcomposition materials such as the metal ammine nitrate oxidizer atelevated temperatures (e.g., temperatures greater than 25° C.), and thusresult in undesirable degradation.

[0041] The presence or inclusion of such potassium perchlorate in thegas generant compositions of the invention has been found to provide orresult in a gas generant composition of sufficiently improvedignitability at −40° C., as compared to a similar composition withoutthe potassium perchlorate gas generant additive, such as to avoid theneed for the presence or inclusion of a charge of igniter materialwithin or in association with the micro-gas generator occupant restraintsystem device 10 That is, gas generant compositions in accordance withthe invention are desirably directly ignitable (e.g., ignitable withoutthe aid of an intermediary igniter material, even at such lowtemperatures. As will be appreciated by those skilled in the art andguided by the teachings herein provided, elimination of the need for thepresence of inclusion of an igniter material can result in significantand substantial simplification of the design and manufacture of devicescontaining such gas generant composition as well as reducing the cost ofmanufacture and production of such devices.

[0042] Further, the presence or inclusion of such potassium perchloratein the gas generant compositions of the invention has also been found todesirably improve the quality of the gas effluent resulting from thereaction thereof, as compared to the gas effluent produced or formedupon combustion of a similar composition without the potassiumperchlorate gas generant additive. More particularly, the potassiumperchlorate additive-containing gas generant compositions of theinvention have been found to produce or result in a gas effluent havinga lesser relative amount of either or both carbon monoxide and one ormore NO_(x) materials, as compared to the gas effluent produced orresulting from the combustion of a similar composition without thepotassium perchlorate gas generant additive.

[0043] One particularly preferred gas generant composition in accordancewith the invention includes:

[0044] between about 25 and about 60 composition weight percentguanidine nitrate,

[0045] between about 10 and about 55 composition weight percent copperdiammine dinitrate,

[0046] between about 2 and about 10 composition weight percent metaloxide burn rate enhancing and slag formation additive selected from thegroup consisting of SiO₂, Al₂O₃ and mixtures thereof, and

[0047] between about 1 and about 20, preferably between about 4 andabout 10, composition weight percent. composition weight percentpotassium perchlorate gas generant additive.

[0048] The initiator 24 and the supply of gas generant composition 30are situated such that upon actuation, the initiator 24 and the supplyof gas generant composition 30 are in reaction-initiating communicationsuch that actuation of the initiator 24 results or otherwise producesreaction of at least a portion of the supply of the gas generantcomposition 30. In the particular illustrated embodiment, the initiator24 and the supply of gas generant composition 30 are in direct contact.

[0049] While the supply of gas generant material 30 is shown as being inthe form of a granular material, it is to be understood that the broaderpractice of the invention is not necessarily limited to theincorporation and use of particular or specific forms of the gasgenerant material. Thus, other suitable forms of gas generant materialsincluding, for example, tablets, grains and wafers, may be used ifdesired.

[0050] Operation

[0051] Typical operation of the micro-gas generator 10, shown in FIG. 1,is as follows:

[0052] Upon the sensing of an occurrence for which actuation of themicro-gas generator 10 is desired, an electrical signal is sent to theinitiator 24. The initiator 24 functions to ignite the supply of gasgenerant material 30 such as to result in the ignition thereof and theformation of a product gas. In those applications where, for example,the micro-gas generator 10 is a seat belt pretensioner, such product gascan be employed to drive a piston to appropriately tighten the seatbelt. The product gas may then be appropriately vented from such pistonassembly, such as into the passenger compartment of the vehicle and suchas known in the art.

[0053] As will be appreciated by those skilled in the art and guided bythe teachings herein provided, gas generant compositions in accordancewith the invention can be processed or otherwise produced by variousmethods. One useful processing technique for gas generant compositionsin accordance with the invention is to simply dry blend the desiredrelative amount of potassium perchlorate with the balance of the desiredgas generant material composition. Alternatively, the desired relativeamount of potassium perchlorate can be incorporated in the gas generantcomposition as an added ingredient during spray dry processing of theformulation such as described in the above-identified related prior U.S.patent applications, now U.S. Pat. No. 6,103,030; U.S. Pat. No.6,083,331; and U.S. Pat. No. 6,224,697, for example.

[0054] The present invention is described in further detail inconnection with the following examples which illustrate or simulatevarious aspects involved in the practice of the invention. It is to beunderstood that all changes that come within the spirit of the inventionare desired to be protected and thus the invention is not to beconstrued as limited by these examples.

EXAMPLES Comparative Example 1 and Example 1

[0055] In each of these tests, a test gas generator device composed ofan assembly such as shown in FIG. 1 and containing the respective gasgenerant formulation shown in TABLE 1, below, at a temperature of −40°C., was deployed into a 10 cubic centimeter closed bomb test tankequipped with a pressure transducer and a high speed data collectionsystem. The pressure in the test tank was recorded as a function of timeand plotted to show a relative comparison of the gas generantcompositions. TABLE 1 GAS GENERANT COMPOSITION (wt. %) ComparativeExample 1 Example 1 guanidine nitrate 42.95 54.72 copper diamminedinitrate 51.95 34.49 silicon dioxide  5.10 4.79 potassium perchlorate —6.00

[0056] The baseline gas generant composition used in Comparative Example1 was a balanced formulation wherein the amount of fuel and oxidizerhave been adjusted to theoretically result, upon combustion, in onlycarbon dioxide, water and nitrogen gas. The formulation of Example 1 wasslightly fuel rich for the purpose of satisfying customer specificationsfor gas effluent concentrations but identical performance results wereobtained with a balanced formulation containing the same amount ofpotassium perchlorate.

[0057]FIG. 2 is a graphical depiction of tank pressure as a function oftime for each of the test inflators of Comparative Example 1 and Example1.

[0058] Discussion of Results

[0059] As shown in FIG. 2, the gas generant composition of Example 1(containing potassium perchlorate in accordance with the invention)burned faster early in the combustion trace and also reached maximumpressure sooner than the baseline formulation of Comparative Example 1.In particular, the formulation containing the potassium perchlorate gasgenerant additive satisfied performance specifications of automakerswhile the baseline formulation did not. Thus, the presence or inclusionof the additive of the invention has been shown as desirably useful toincrease gas generant material performance to meet automakerspecifications.

Comparative Example 2 and Example 2

[0060] In these tests, a heavyweight test hardware fixture containing a32 gram load of the respective balanced gas generant compositions shownin TABLE 2, below was fired into a 60 liter tank, with the gas effluentstherein measured by FTIR. The results are shown in TABLE 3, below.

[0061] In the composition of Example 2, the potassium perchlorate wasdry blended into a spray dried formulation containing the otheringredients. TABLE 2 Composition (wt. %) Comparative Example 2 Example 2guanidine nitrate 42.95 45.63 copper diammine dinitrate 51.95 45.48silicon dioxide  5.10 4.89 potassium perchlorate — 4.00 EquivalenceRatio  1.00 1.00

[0062] TABLE 3 EFFLUENT (ppm) TEST CO NO NO₂ Comparative Example 2 67309903 1849 Example 2 2717 3525  342

[0063] Discussion of Results

[0064] Both compositions were formulated to only produce carbon dioxide,water and nitrogen gas upon combustion. The combustion temperatures forboth compositions were similar enough to each other to rule out atemperature effect on effluent concentrations.

[0065] As shown in TABLE 3, the potassium perchlorate-containing gasgenerant composition of Example 2 and in accordance with the inventionexhibited, upon combustion, a reduction in both those effluent specieswhich are fuel-rich (e.g., carbon monoxide) and those effluent specieswhich are oxygen-rich (e.g., NO_(x)).

[0066] Thus, the invention provides an improved gas generant compositionparticularly suited for use in micro-gas generator devices such as forseat belt pretensioning as well as corresponding or associated improvedgas generation devices, systems and methods. In particular, the gasgenerant compositions of the invention, in addition to satisfyingrequirements for applications such as in micro-gas generator occupantrestraint system devices such as seat belt pretensioners, such asrequirements relating to flame temperature and gas output, desirably aredirectly ignitable that is they avoid a need or requirement for thepresence or inclusion of an auxiliary pyrotechnic compound, such as anigniter, in order to meet performance requirements such as relating tolow temperature operation (e.g., operation at temperatures belowambient, e.g., 25° C., to as low as about −40° C., for example).Further, the invention generally provides such gas generant compositionswhich desirably produce or result in gaseous effluents having a suitablyreduced or lower contents of undesired effluent gases such as carbonmonoxide and NO_(x), for example, as compared to similar compositionsbut which lack the potassium perchlorate gas generant additive of theinvention.

[0067] The invention has been described above with reference toparticular embodiments wherein the gas generant composition of theinvention is employed within a micro-gas generator occupant restraintsystem device. It is to be understood, however, that such gas generantcompositions of the invention can, if desired, be utilized or employedin other suitable or appropriate occupant restraint system devices, aswill be apparent to those skilled in the art and guided by the teachingsherein provided.

[0068] The invention illustratively disclosed herein suitably may bepracticed in the absence of any element, part, step, component, oringredient which is not specifically disclosed herein.

[0069] While in the foregoing detailed description this invention hasbeen described in relation to certain preferred embodiments thereof, andmany details have been set forth for purposes or illustration, it willbe apparent to those skilled in the art that the invention issusceptible to additional embodiments and that certain of the detailsdescribed herein can be varied considerably without departing from thebasic principles of the invention.

What is claimed is:
 1. A gas generant composition comprising: betweenabout 25 and about 60 composition weight percent non-azidenitrogen-containing gas generating fuel; between about 10 and about 55composition weight percent metal ammine nitrate oxidizer; between about0 and about 50 composition weight percent ammonium nitrate supplementaloxidizer component; between about 2 and about 10 composition weightpercent metal oxide burn rate enhancing and slag formation additive; andbetween about 1 and about 20 composition weight percent potassiumperchlorate gas generant additive.
 2. The gas generant composition ofclaim 1 wherein the composition has improved ignitability as compared toa similar composition without the potassium perchlorate gas generantadditive.
 3. The gas generant composition of claim 1 wherein, uponcombustion, the composition produces a gas effluent having a lesserrelative amount of NO_(x) as compared to a gas effluent upon combustionof a similar composition without the potassium perchlorate gas generantadditive.
 4. The gas generant composition of claim 1 wherein, uponcombustion, the composition produces a gas effluent having a lesserrelative amount of carbon monoxide as compared to a gas effluent uponcombustion of a similar composition without the potassium perchlorategas generant additive.
 5. The gas generant composition of claim 1wherein the non-azide nitrogen-containing gas generating fuel comprisesguanidine nitrate.
 6. The gas generant composition of claim 1 whereinthe metal ammine nitrate oxidizer comprises copper diammine dinitrate.7. The gas generant composition of claim 1 wherein the metal oxide burnrate enhancing and slag formation additive is selected from the groupconsisting of SiO₂, Al₂O₃ and mixtures thereof.
 8. The gas generantcomposition of claim 1 wherein the potassium perchlorate gas generantadditive is present in an amount of between about 4 and about 10composition weight percent.
 9. A seat belt pretensioner containing thegas generant composition of claim
 1. 10. An occupant restraint systemdevice containing the gas generant composition of claim
 1. 11. A gasgenerant composition comprising: between about 25 and about 60composition weight percent guanidine nitrate; between about 10 and about55 composition weight percent copper diammine dinitrate; between about 0and about 50 composition weight percent ammonium nitrate supplementaloxidizer component; between about 2 and about 10 composition weightpercent metal oxide burn rate enhancing and slag formation additiveselected from the group consisting of SiO₂, Al₂O₃ and mixtures thereof;and between about 1 and about 20 composition weight percent potassiumperchlorate gas generant additive.
 12. The gas generant composition ofclaim 11 wherein the composition has improved ignitability as comparedto a similar composition without the potassium perchlorate gas generantadditive.
 13. The gas generant composition of claim 11 wherein, uponcombustion, the composition produces a gas effluent having a lesserrelative amount of NO_(x) as compared to a gas effluent upon combustionof a similar composition without the potassium perchlorate gas generantadditive.
 14. The gas generant composition of claim 11 wherein, uponcombustion, the composition produces a gas effluent having a lesserrelative amount of carbon monoxide as compared to a gas effluent uponcombustion of a similar composition without the potassium perchlorategas generant additive.
 15. The gas generant composition of claim 11wherein the potassium perchlorate gas generant additive is present in anamount of between about 4 and about 10 composition weight percent.
 16. Aseat belt pretensioner containing the gas generant composition of claim15.
 17. A seat belt pretensioner gas generant composition comprising:between about 25 and about 60 composition weight percent guanidinenitrate; between about 10 and about 55 composition weight percent copperdiammine dinitrate; between about 0 and about 50 composition weightpercent ammonium nitrate supplemental oxidizer component; between about2 and about 10 composition weight percent metal oxide burn rateenhancing and slag formation additive selected from the group consistingof SiO₂, Al₂O₃ and mixtures thereof; and between about 4 and about 10composition weight percent potassium perchlorate gas generant additive.18. The seat belt pretensioner gas generant composition of claim 17wherein the composition has improved ignitability as compared to asimilar composition without the potassium perchlorate gas generantadditive.
 19. The seat belt pretensioner gas generant composition ofclaim 17 wherein, upon combustion, the composition produces a gaseffluent having a lesser relative amount of NO_(x) as compared to a gaseffluent upon combustion of a similar composition without the potassiumperchlorate gas generant additive.
 20. The seat belt pretensioner gasgenerant composition of claim 17 wherein, upon combustion, thecomposition produces a gas effluent having a lesser relative amount ofcarbon monoxide as compared to a gas effluent upon combustion of asimilar composition without the potassium perchlorate gas generantadditive.
 21. A method of generating gas suitable for use in an occupantrestraint system of a motor vehicle, said method comprising: directlyigniting a reactant material including a fuel component containingbetween about 25 and about 60 composition weight percent of a non-azidenitrogen-containing gas generating fuel, between about 10 and about 55composition weight percent metal ammine nitrate oxidizer, between about0 and about 50 composition weight percent ammonium nitrate supplementaloxidizer component, between about 2 and about 10 composition weightpercent metal oxide burn rate enhancing and slag formation additive, andbetween about 1 and about 20 composition weight percent potassiumperchlorate gas generant additive.
 22. The method of claim 21 whereinthe reactant material has improved ignitability as compared to a similarcomposition without the potassium perchlorate gas generant additive. 23.The method of claim 21 wherein, upon combustion, the reactant materialproduces a gas effluent having a lesser relative amount of NO_(x) ascompared to a gas effluent upon combustion of a similar reactantmaterial without the potassium perchlorate gas generant additive. 24.The method of claim 21 wherein, upon combustion, the reactant materialproduces a gas effluent having a lesser relative amount of carbonmonoxide as compared to a gas effluent upon combustion of a similarreactant material without the potassium perchlorate gas generantadditive.
 25. The method of claim 21 wherein the potassium perchlorategas generant additive is present in the reactant material in an amountof between about 4 and about 10 composition weight percent.